Archive for the ‘Do It Yourself’ Category:

2020-03-10 Simple AM Band Antenna Tuning Coil 240 Microhenrys

The standard ferrite antenna loopstick for a 365 pF tuning capacitor has an inductance of about 230 microhenrys. This in combination with the tuning capacitor tunes across the full AM broadcast band. It’s useful to be able to wind your own inductor so it can be used for an antenna coil, a trap to attenuate

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2020-01-23 DIY Variable Capacitor 90 to 3400 pF

The beginning isn’t clear about how it looks. First, scroll to end and look at the photo. https://www.randombio.com/capacitor.html

2020-01-02 Coax Cable and Crimp-On Connectors

FB comment Years ago at work (community college) we had an IBM mainframe and the terminals were connected with coax cables. We also had thin Ethernet cabling. I had the proper connectors and thousand foot boxes of coax, and most importantly the proper stripping and crimping tools. I installed hundreds of coaxes, and I was

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2018-08-29 High Temperature And Nylon Screws

From FB group Hobby Electronics, 2018-09-01 I faced this dilemma before. I’ve repaired power supplies where the transistor failed because it was not held tightly to the heat sink because of a nylon screw that got hot. I used a steel screw and a fiber washer, and heat shrink tubing over the threads to insulate.

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2018-03-02 One Transistor AM Radio

FB group Building Transistor Radios In JF1OZL’s voluminous archive I found his version of a MW receiver.  It is labeled [2] …. MW-RADIO (see link).  He used a long wire antenna, and an IF transformer with the ceramic capacitor removed for the tuning coil.  He also said to use a ferrite loopstick, which is what

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2018-01-08 RF Oscillator For AM Band

For FB group Building Transistor Radios When I started building regen receivers, the first thing I found I needed was a simple  signal generator.  I have a function generator, but every time I want a different frequency, I had to readjust the controls.  So I built a few RF oscillators to put close to the

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2017-09-01 Automated Gallows РArduino 

Suggestion for project on FB group Arduino Projects – Sept 17 Automated Gallows! A motorized winch adjusts noose. Asks for three officials to each press confirmation button. Has an emergency abort button. Counts down 5, 4, 3, 2, 1… Pulls the trapdoor latch! Monitors heartrate until no sign for 5 minutes Lights up sign “Execution

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2016-12-05 Regenerative Receiver

After I unsoldered the parts from my failed ‘noisy regenerative receiver’ circuit, I decided to build a more conventional regenerative receiver, one that uses a single transistor for the regenerative stage. I chose the circuit from a website that I had found, and saved the schematic. But I forgot to document the URL of the

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